Abstract: Insulation monitoring of a direct current power supply system is achieved by application of an alternating current and the detector is constituted by a current transformer and a Hall-effect current sensor. This Hall-effect sensor controls a direct current generator, which supplies a compensation winding of the current transformer, so as to prevent saturation of the toroid of this current transformer. When a ground fault occurs, the alternating current generator generates a fault current detected by the transformer.

Abstract: A digital isolation monitor comprises a signal processor operating in conjunction with a measuring circuit to perform a first no-load measurement and a second load measurement of a zero sequence signal delivery by a toroid of a differential transformer, followed by synchronous demodulation, A microcontroller computes the tangent of the angle of phase difference introduced by the toroid by computing the relationship between the load and no-load components, and determines the true values of the leakage resistance and stray capacitance of the power system.

Abstract: A plug-mounted wriststrap detector and ground monitor includes hot, neutral and ground input terminals which are connected to corresponding terminals of a power outlet when the circuit is plugged in. A jack is provided to plug a wriststrap into the circuit to provide electrostatic protection to the user. Means are provided to detect that the user is wearing the wriststrap and that the wriststrap is properly connected to the circuit as a function of whether an a.c. signal of sufficient amplitude is detected coupled to the circuit by the wriststrap and/or user. Lamps and an audible alarm warn the user if the wriststrap is not properly connected. A precision ground integrity circuit is provided to detect whether an unsafe ground condition exists and to alert the user accordingly. The ground integrity circuit uses a constant current source and voltage comparator to determine that the ground impedance does not exceed a predetermined limit.

Abstract: The present invention is a monitor that detects generator core 12 hot spots where the insulation between ferromagnetic sheets is breaking down by monitoring rotor 10 shaft voltage. The difference between the differential shaft voltage at each end of the rotor 14 produces a voltage signal that changes as the core 12 malfunctions. By comparing signal samples over time, core failure can be detected. Spring loaded rotor shaft brushes 20 and 22 connected to differential isolation amplifiers 24 and 26 obtain the voltage between ends 16 and 18 of the rotating shaft and nearby frame, and a differential amplifier 28 produces the difference between the shaft end differential voltages which is the shaft dissymmetry voltage. An analog-to-digital converter 30 produces digital values of the dissymmetry voltage which can be converted into a voltage frequency spectrum by a Fourier Transform routine executed by a computer 32 or analyzed directly.

Abstract: A system for monitoring a grounding system is permanently installed in, for example, a telephone switching office. The system operates to scan a large number of ground conductors at the master ground bar by using amplified Hall effect sensors to monitor AC and DC current on the conductors. If a surge enters the telephone switching office, the surge is coupled to ground. The system monitors these ground conductors to insure that the ground system is operating properly. The microprocessor continuously insures that readings are taken of the current on each of the ground conductors. The microprocessor compares the current readings with preset parameters. If a reading exceeds the predetermined parameter threshold, an alarm report is generated. The report lists not only the current on the conductor which was the source of the surge, but also shows any current increase on the other ground conductors that are monitored.

Abstract: When equipped with this improvement, a Gound Fault Circuit Interrupter will continue to monitor its protected circuits after tripping and automatically reset itself to restore power when no fault conditions are detected or when detected faults do not exceed a predetermined conduction level and are determined to be non-hazardous. The reset circuit shunts the tripped GFCI relay to pass a safely limited test current into the otherwise disconnected circuits of electrical utilization devices to determine the absence or the extent of fault conditions and is substantially fail-safe in regard to its own function. Four of the embodiments show the circuit as incorporated into the circuitry of an electrically resettable GFCI and a fifth as contained within an attachable enclosure.

Abstract: A direct current fan's status is monitored electronically using a current monitoring circuit. Normally, when a fan is running it exhibits a pulsating current input. The resulting alternating current signal is monitored via the current monitoring circuit to detect whether the fan is running or not.

Abstract: A method and apparatus for determining the existence of an undesired connection between an electrical system and a desired single-point ground. The electrical system is first disconnected from the desired single-point ground, and is connected to the center point of a resistive divider connected to an isolated voltage source. The voltage of the center point of the resistive divider is monitored and an indication is provided if the monitored voltage indicates the existence of undesired ground paths. The invention also includes elements for measuring the resistance value of a detected undesired ground path, thereby facilitating identification and removal thereof. The invention also includes a voltage clamp which is placed between the electrical system and the desired single-point ground when the electrical system is disconnected from the single-point ground.

Abstract: A method and apparatus for testing three wire handheld soldering irons by touching the iron's tip to a single point sensor to measure (1) tip temperature (2), tip voltage to ground and (3) tip resistance to ground.

Abstract: In a ground circuit apparatus for electronic equipment according to this invention, a motor driving circuit group constituted of a drum motor, a loading motor and a capstan motor is connected with a DC power source through a power source line and a ground line to have power supplied therefrom. A signal processing circuit group constituted of a camera circuit, a logic circuit, servo circuit, video circuit and an audio circuit as well as an electronic view finder is connected with the DC power source through the power line and a ground line. A video circuit of the signal processing circuit group is connected through a ground line to a chassis which serves as a reference potential point. In addition, two diodes connected in parallel and directed in mutually opposite directions to have opposite polarities and a ground line are connected between the electronic view finder and the chassis.

Abstract: A generator for subjecting an electrical apparatus to a surge voltage. The generator includes a surge voltage generator, a line isolation surge filter, wave shaping circuits and a rectifier coupling network for coupling the surge voltages in shunt with the power line and the equipment under test.

Abstract: A system for detecting and locating a ground fault (34) in the field winding (2) of a machine, in which a DC potential is present across the winding (2) during machine operation and the winding (2) is normally insulated from ground, the system including: a voltage divider (4) connectable in parallel with the winding (2) and having a plurality of tap points spaced apart along the divider (4); a plurality of current paths (6, 8, 14) each connected between a respective tap and a ground connection point (16); a current detector (12) connected in the current paths (6, 8, 14) for providing an indication of the magnitude of current flowing through each path (6, 8, 14); and signal processing circuitry (20, 22, 24) connected to the current detector (12) for providing an indication of the occurrence of a current flow magnitude associated with a ground fault (34) in the field winding (2) and an indication of at least the approximate location of the ground fault (34 ) along the winding (2).

Abstract: It is known to detect a single breakdown of the electrical insulation separating the rotor winding from the earthed rotor body of a generator: such a failure does not lead to intense arcing, however, as there is no return path for current flowing to earth. Disclosed is a potential divider network which allows continuous monitoring of the voltages between earth and the two ends of the winding: a second breakdown can be rapidly detected since it results in a shift in both the position and magnitude of the effective resistance to earth from that associated with the first breakdown.

Abstract: An earth testing means for monitoring the status of the earth return system of an electric fence network is arranged to indicate the potential difference between the earth return system of the electric fence and a secure earth. In one embodiment the earth testing means comprises an indicator to provide a quantitive display of the fence earth-secure earth potential difference.

Abstract: A marking tape that is positioned underground above utility lines wherein the marking tape carries a pair of closely spaced, parallel, insulated conductors that extend the length of the tape and at least one other insulated conductor extending the length of the tape which is separated from the pair of conductors at a distance that is greater than the distance between the conductors of the pair of conductors. Passive markers having a resonant circuit can be selectively placed along the tape wherein the resonant circuit is electromagnetically coupled to the pair of conductors and the other conductor. The other insulated conductor can be one of a pair of conductors similar to the other pair of conductors. A method is disclosed whereby the making tape can be electromagnetically traced with the position of the passive markers established. A method is also disclosed for determining the distance to a break in the tape which causes the pair of conductors to be severed.

Abstract: A ground fault simulation is produced responsive to a pool or spa water overtemperature condition, tripping the ground fault interrupter and shutting down the pump used to recirculate the water.

Abstract: A phase shifter uses a PIN diode or diode pairs operated in a switching mode to switch transmission-line elements for phase-shifting radio frequency or microwave signals. A drive circuit for each diode(s) includes a FET switch controlled by a first level of a bilevel control signal to apply B+ to forward bias the diode(s) with a forward current. When forward biased, the active region of the diode(s) becomes flooded with charge carriers. The first FET switch is turned OFF by a second level of the bilevel control signal, and a second FET switch is turned ON to apply a reverse bias voltage to the diode(s) to render them nonconductive. Before the diode(s) become nonconductive, the excess charge carriers must be swept out of the diode(s). To achieve fast switching, the second FET switch must draw a large current for a short time as the excess charge carriers are removed.

Abstract: A test system for microwave circuits such as employed in aircraft wherein a plurality of antennas are connected to a single processor whereby the continuity of the antennas and connectors between the antennas and the processor can be determined. A test signal is applied to the various antennae of the aircraft and the return signals therefrom received by a test antenna disposed in conjunction with a low-loss coupler from outside of the aircraft. An automated test circuit provides for inputting an identifier of the antenna and circuit portion being tested, and for determining the fault location within the circuit as a function of the circuit portion under test and the distance to the fault; and for displaying the fault location within the circuit. In one embodiment, the low-loss coupler includes the use of a plurality of test antennas in combination with a divider circuit connected to the test antennas by transmission lines.

Abstract: An elastomeric belt and hose conductivity testing device incorporating a comparator network to verify that a belt or hose is either conductive or nonconductive (resistive) of the flow of static electricity. The device indicates whether the article being tested has a resistivity or conductivity which meets the industry standard of resistivity or conductivity for that particular article. The testing device is battery powered so that it is easily portable for use in the field.

Abstract: An apparatus for measuring the transit time of electromagnetic waves has a pulse generator (11) which is arranged in a feedback loop (12) and which can be triggered by pulses. Either the measurement path (13) or a reference path (14) with a reference receiver (16) at the end of it can be selectively included in the feedback loop (12). The pulse generator is also connected to a computing/counting stage (19) which counts the pulse transmitted during the measurement and reference periods separately and computes the transit time therefrom (FIG. 1).

Abstract: Wire identifying apparatus for identifying wires of a multiple wire electrical system as the wires extend between one location and another, said wire identifying apparatus comprising two separate units for use at the two locations, respectively, and designated herein as Unit No. 1 and Unit No. 2, Unit No. 2 having a plurality of terminals for connecting to one end of the wires to be identified and having a ground terminal, Unit No. 2 also having an array of resistors connected in parallel circuit with each other between the ground terminal and the other terminals, there being a different resistor corresponding to each of the other terminals, Unit No. 1 having a plurality of terminals for connecting to the opposite end of the wires to be identified and having a ground terminal, Unit No. 1 also having electrical circuitry including a selector switch having multiple positions corresponding to the number of terminals on Unit No.

Abstract: Test circuitry is included in a PROM memory for detecting shorts between bit lines and word lines and shorts or leaks in a memory cell. The circuitry enables a selected positive voltage to be applied across all memory cells in the memory so that the existence of leaky memory cells or shorts in the memory can be detected during testing. The test circuitry has no appreciable effect on the memory during normal operation of the memory.

Abstract: An automobile circuit tester is provided having an end connection receivable in the taillight socket, parking light socket, brake light socket or directional signal socket in place of the bulb. When a circuit is completed to the socket in which the tester is received, an audible signal is generated.